import org.apache.commons.codec.binary.Base64;
import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;


public class shiyan3_4 {
	//存放公私钥
	private static Map<Integer,String> keyMap = new HashMap<Integer,String>();
	public static void main(String[] args) throws Exception {
		//生成公钥和私钥
		funcGetKey();
		//加密字符串
		String message = "hello world";
		System.out.println("随机生成的公钥为:" + keyMap.get(0));
		System.out.println("随机生成的私钥为:" + keyMap.get(1));
		String messageEn = encrypt(message,keyMap.get(0));
		System.out.println(message + "\t加密后的字符串为:" + messageEn);
		String messageDe = decrypt(messageEn,keyMap.get(1));
		System.out.println("还原后的字符串为:" + messageDe);
	}
	public static void funcGetKey() throws NoSuchAlgorithmException {
		KeyPairGenerator keyPai = KeyPairGenerator.getInstance("RSA");
		keyPai.initialize(1024,new SecureRandom());
		KeyPair keyP = keyPai.generateKeyPair();
		RSAPrivateKey priKey = (RSAPrivateKey)keyP.getPrivate();
		RSAPublicKey pubKey = (RSAPublicKey)keyP.getPublic();
		String publicKeyString = new String(Base64.encodeBase64(pubKey.getEncoded()));
		// 得到私钥字符串  
		String privateKeyString = new String(Base64.encodeBase64((priKey.getEncoded())));
		// 将公钥和私钥保存到Map
		keyMap.put(0,publicKeyString);  //0表示公钥
		keyMap.put(1,privateKeyString);  //1表示私钥

	}

	public static String encrypt( String str, String publicKey ) throws Exception{
		//base64编码的公钥
		byte[] decoded = Base64.decodeBase64(publicKey);
		RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
		//RSA加密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, pubKey);
		String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
		return outStr;
	}

	public static String decrypt(String str, String privateKey) throws Exception{
		//64位解码加密后的字符串
		byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
		//base64编码的私钥
		byte[] decoded = Base64.decodeBase64(privateKey);  
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));  
		//RSA解密
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, priKey);
		String outStr = new String(cipher.doFinal(inputByte));
		return outStr;
	}

}
